1. Field of the Invention
The present invention relates to a transducer which is used in a bonding apparatus and to a bonding apparatus which is structured to include the transducer.
2. Prior Art
In a bonding apparatus including wire bonding apparatuses, a transducer such as an ultrasonic horn and the like is used. Bonding is accomplished by applying a load and ultrasonic vibrations to the bonding section of the horn by causing the transducer to vibrate in the lengthwise direction (axial direction) of the transducer by a vibrator and at the same time by lowering a bonding tool mounted at the tip end of the transducer toward the object of process (bonding) and applying a load thereto.
A conventional supporting structure for such a transducer used in a wire bonding apparatus (not shown) is shown in FIG. 10.
In this transducer, a capillary 166 used as a bonding tool. The capillary 166 is attached to the tip end of an ultrasonic horn 151 that is used as a transducer, and a wire (not shown) passes through the capillary 166. An ultrasonic vibrator 90 is fastened to the base end of the ultrasonic horn 151. A flange 154 which has a cylindrical shape and is connected to the ultrasonic horn 151 at the front end of said flange 154 is disposed on the ultrasonic horn 151. The flange 154 is provided so that it is at a node (i.e., a point where the strain reaches the maximum) position of the ultrasonic vibration, which is applied as a compressional wave (longitudinal wave) in the axial direction, i.e., the direction of length of the horn 151. The flange 154 is connected to a cylindrical horn support 155. The horn support 155 is fastened to a transducer holder 156, and this transducer holder 156 is fastened to a supporting shaft 157. The supporting shaft 157 is supported on a bonding head (not shown) of the bonding apparatus either directly or via a lifter arm, so that the supporting shaft 157 is free to rotate.
Wire bonding apparatuses of this type are disclosed in, for example, Japanese Patent Application Laid-Open (Kokai) Nos. 5-347334, 6-196532 and 10-303240.
In the above prior art, the flange 154 is disposed at a node position of the ultrasonic vibration in the ultrasonic horn 151. Accordingly, the energy loss (so-called leakage) via this flange 154 is small; and thus, a defective crushed shape of the ball, stripping of the ball or damage to the substrate, etc., caused by the continued application of unnecessary ultrasonic energy following the completion of bonding can be prevented.
However, as the operation of the bonding apparatus is performed at higher speeds, oscillation during the raising and lowering movement of the transducer becomes a problem. In this respect, since the ultrasonic horn 151 in the above prior art is supported at only one place, it is difficult to effectively suppress the oscillation of the transducer caused by the operation of the bonding head. When such oscillation occurs, an excessive force is applied to the ball during bonding, and defects in the crushed shape of the ball occur. This problem is especially conspicuous in the diameters of press-bonded balls that have been reduced as a result of the increasingly finer pitch of recent semiconductor devices.
In order to deal with oscillation of the transducer during the raising and lowering movement of the transducer, the applicant of the present invention has proposed in Japanese Patent Application Laid-Open (Kokai) No. 2001-24025 a transducer structure as shown in FIG. 11.
In this structure, an ultrasonic horn 201 used as a transducer is attached to a transducer holder 206 via two horn supporting members 205 that are separate elements from the ultrasonic horn 201. The attachment positions of the horn supporting members 205 in the axial direction of the ultrasonic horn 201 are adjustable. In this structure, since there are two supporting points, oscillation during the raising and lowering movement of the ultrasonic horn 201 can be effectively prevented. Furthermore, a loss of the ultrasonic vibration (compressional wave) in the axial direction of the horn can also be prevented by causing the attachment positions of the horn supporting members 205 with respect to the ultrasonic horn 201 to coincide with node positions of the vibration of the ultrasonic horn 201.
Incidentally, as the regions where the horn supporting members (horn supporting members 205 in the structure of FIG. 11) are connected to the ultrasonic horn become larger (thicker) in the direction of length of the ultrasonic horn, the portions of these regions that are away from the nodes of the vibration increase. As a result, there is a corresponding increase in the energy loss. More specifically, in order to reduce the energy loss that occurs via the horn supporting members, it is desirable to form the horn supporting members as thin as possible in the axial direction of the ultrasonic horn. However, if the horn supporting members are thin, then there is a corresponding drop in the strength of the horn supporting members.
Furthermore, in the structure in which the ultrasonic horn 151 is supported at a single point as shown in FIG. 10, the cutting work for forming the cylindrical flange 154 into a cylindrical shape that is open at one end is difficult, and it is also difficult to reduce the size of the ultrasonic horn 151. Moreover, in the structure that uses two horn supporting members 205 that are independent elements from the ultrasonic horn 201 as shown in FIG. 11, the total number of parts increases, and assembly becomes bothersome.
Accordingly, the object of the present invention is to provide a transducer having a structure that provides the supporting members of the transducer with strength and that makes it possible to form such supporting members as thin as possible in the axial direction of the transducer.
The above object is accomplished by a unique structure for a transducer which is caused to vibrate by an operation of a vibrator, and the transducer of the present invention comprises: holding portions which are provided in at least two areas that include nodes (or node positions) of vibration in a transducer main body, and connecting portions that connect the holding portions to each other at areas that differ from areas where the holding portions protrude from the transducer main body; and further the transducer main body, the holding portions and the connecting portions are integrally formed from a single material member, and a tool that performs a treatment action such as bonding is located at a vibration crest, and such a tool can be disposed outside the region that is located between at least two holding portions or inside the region that is located between at least two holding portions.
In the structure of the above-described transducer of the present invention, the holding portions are disposed in at least two areas that include nodes of vibration in the transducer main body. Accordingly, oscillation of the transducer is prevented without causing a vibrational energy loss in the axial direction of the transducer. Furthermore, in the transducer of the present invention, the connecting portions that connect the holding portions to each other are provided at areas that differ from areas where the holding portions protrude from the transducer main body. Accordingly, the external force applied to one of the holding portions is dispersed in each of the respective holding portions connected by the connecting portions, deformation of the holding portions is prevented, and the respective holding portions can be formed extremely thin in the axial direction of the transducer main body.
Furthermore, since the transducer main body, holding portions and connecting portions are formed integrally from the same member, a sufficient strength is secured at the connection areas between the holding portions and the transducer main body, and the holding portions can be made even thinner.
In addition, when the tool that performs the treatment action is disposed inside the region that is located between the two holding portions, it is preferable that such holding portions are installed in two places, and a chip suction-chucking port is installed at an intermediate point between the points where these holding portions are provided. With this structure, the load distribution on the chip suction-sucking port can become evened.
When the above-described transducer is used in a bonding apparatus, the advantages and effect described above with reference to the transducer are obtained.